OMA Protocol Review: OMAMAN-56 Sulfites in Shrimp

Table 2. Selectivity Results

Direct measure of the compounds at 100 ppm

Raw head on shrimp

Raw head on Recovery (%)

Raw head off shrimp

Raw head off Recovery (%)

Boiled shrimp Recovery (%)

Boiled shrimp

Compound, 100 ppm

98

89 90 91 81 87

91 87 93 85 84

100

103

98 99

100

Sodium sulfite Sodium bisulfite

104

94 93 87 89

91 95 91 86

96

98 96

101 100

104 104

Sodium metabisulfite Potassium metabisulfite

103

94

91

Formaldehyde- bisulfite adduct

0 0

0 0

- -

0 0

- -

0 0

- -

Methionine

Cysteine

No matrix effects or cross-reactivity to sulfur-containing amino acids were found.

Matrix Study

(a) Methodology.- The Biofish-300 SUL method was compared to OMA 990.28, the optimized Monier-Williams method for determination of sulfites in foods (4) for calculation of accuracy and bias using both incurred shrimp and fortified shrimp. Incurred shrimp: For each matrix (raw head-on, raw head-off, and boiled shrimp), 3 lots of product known to contain sulfites were obtained. Three hundred g of each lot were mixed and three 50- g test portions were weighed out for the OMA method and five 2-g test portions for the Biofish method. Each 2-g blind coded test portion was extracted and analyzed according to the Biofish method as detailed above (see sample preparation) and each 50-g blind coded test portion was analyzed according to the OMA 990.28 method (4). Fortified shrimp: The method developer laboratory obtained 2000 g of raw head-off, raw head- on and boiled shrimp with no sulfite added. Four sodium metabisulfite solutions were prepared such that three concentrations of fortified shrimp extending across each range of the Biofish method were prepared. The following method was used to fortify shrimp at each concentration: Submerge and swirl shrimp in metabisulfite solution and transfer to colander to drain without rinsing. From each fortified batch and from the unfortified matrix, three 50-g test portions for the OMA method were weighed out and five 2-g test portions for the Biofish method were weighed out. The Biofish method was repeated on a second day using a second analyst. Recovery experiment: Each matrix was examined sulfite-free and fortified at 3 concentrations (50, 100, and 250 mg/kg) with sodium metabisulfite using the following method: fixed amounts of raw head-off, raw head-on and boiled shrimp with no sulfite added were peeled and minced, and inoculated with the known concentration of sodium metabisulfite. The Biofish method was performed on blinded replicate 2-g test portions and was repeated on a second day with a second analyst. Results were

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